在Ruby中定义全局方法的方法 | 在Ruby中定义全局方法的方法

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问题描述

我正在写一个小宝石，我想定义一个类似于DSL的方法，与 Rake 中的desc和task方法几乎相同.

I'm writing a small gem, and I want to define a DSL-like method, pretty much the same as the desc and task methods in Rake.

Rake在Rake::DSL模块中，然后在

Rake defines them as private methods in the Rake::DSL module and then

self.extend Rake::DSL

将模块混入主要对象中? (我是新手，如果我输入错了，请继续大笑)

to mix the module into the main object? (I'm a newbie and go ahead laugh if I'm wrong)

这样做有什么好处?是因为将这些方法设为私有可以阻止其他任何对象使用它们(也就是说，防止类似some_obj.desc的东西)?

what are the benefits by doing so? is it because making these methods private can prevent any other objects to use them (that is, to prevent something like some_obj.desc) ?

如果在Kernel

module Kernel
  private

  include Rake::DSL
end

有什么区别吗?

推荐答案

只是为了扩展bor1s给出的关于 private 方法的答案:

Just to extend the answer given by bor1s, about the private methods:

在红宝石中，您有私有"和受保护"的方法.当谈论保护"方法时，bor1s所说的是正确的.将方法声明为私有"还可以防止同一类的其他实例使用该方法.

In ruby you have "private" and "protected" methods. What bor1s says, is correct when talking about "protected" methods. Declaring a method "private" additionally prevents other instances of the same class from using the method.

调用私有"方法时，不能在其前面使用圆点-甚至不能使用self.，即使使用或省略self通常具有相同的效果.

When you call a "private" method, you cannot use a dot in front of it - you cannot even use self., even though using or omitting self has usually the same effect.

class Xyzzy
  private
  def foo
    puts "Foo called"
  end

  public
  def do_it
    foo       # <= Is OK
    self.foo  # <= raises NoMethodError
  end
end

Xyzzy.new.do_it

如果在上面的代码中将专用"更改为受保护"，则不会出现任何错误.

If you change 'private' to 'protected' in the code above, no error will be raised.

关于模块:

在Kernel中定义方法并使用某些模块中定义的方法扩展Kernel的最终结果是相同的:在两种情况下，该方法都是全局的.

The final result of defining a method in Kernel and extending Kernel with the method defined in some module is the same: in both cases the method is global.

使用模块稍微优雅一点，因为它可以将您的变化集中在一个地方，但是我要说这是个人喜好的问题.

Using a module is just a little more elegant, as it groups your changes in one place, but I would say it's a matter of personal taste.

通常，您不在内核或对象中包括方法(因为这可能有些危险)，但是您包括(或扩展)需要这些方法的特定类或对象，在这种情况下，您需要将您的方法归为一个模块.

Usually you do not include methods in Kernel or Object (as it may be a little dangerous), but you include (or extend) a specific class or object which needs these methods, and in this case you need your methods grouped in a module.

0.9.0版中的Rake甚至停止了在Object中包含DSL命令:

Even Rake in version 0.9.0 stopped including the DSL commands in Object:

不兼容 *更改*:Rake DSL命令(任务"，文件"等)是不再是Object中的私有方法.如果您需要在内部调用"task:xzy" 您的课程中，将Rake :: DSL包含在课程中. DSL仍然可以在以下位置使用顶层范围(通过扩展Rake :: DSL的顶层对象).

Incompatible *change*: Rake DSL commands ('task', 'file', etc.) are no longer private methods in Object. If you need to call 'task :xzy' inside your class, include Rake::DSL into the class. The DSL is still available at the top level scope (via the top level object which extends Rake::DSL).

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